The present invention relates generally to apparatus for use in severing predetermined lengths of stock from a workpiece and more particularly to such apparatus which is operative to sever predetermined lengths of tubing from a continuously moving workpiece.
In order to increase manufacturing speed, apparatus has been developed which is capable of severing predetermined lengths of tubing from a continuously moving supply. Such apparatus, more commonly known as flying cutoff machines, generally include a reciprocating carriage assembly having a cutting assembly mounted thereon and suitable motor means such as an electric motor adapted to rotatably drive the cutting assembly. Typically the motor is mounted on the carriage assembly adjacent but offset from the path of travel of the workpiece and the axis of rotation of the cutting assembly. Mechanical means, such as belts and pulleys, gears, or the like, are provided to transmit the rotational forces from the motor to the cutting assembly. While such mechanical power transmission devices are fully operable, the use thereof significantly increases the total mass which must be reciprocated in order to provide a flying cutoff capability. Because the rate of acceleration of an object is inversely proportioned to the mass to be accelerated, this increased mass significantly reduces the maximum speed of operation of the machine. Further, such devices require periodic maintenance and, as with any operative device, are subject to potential failure both of which may result in increased operating costs and downtime.
In order to reciprocate the cutting means into and out of engagement with the workpiece, various gear and cam drive arrangements have been utilized along with suitable timing mechanisms operative to synchronize the actuation thereof. However, again such gear and cam drive arrangements require numerous parts and associated supporting structure all of which operate to increase the mass which must be reciprocated and thus may reduce the operating speed of the apparatus. Further, such arrangements may require periodic lubrication and inspection for wear so as to insure proper synchronized actuation thereof thus resulting in increased maintenance costs.
The present invention, however, overcomes these disadvantages by providing a relatively simple efficient tube cutting apparatus of the flying cutoff type which has a cutting assembly directly connected to the shaft of the driving motor. The motor shaft is provided with a bore extending therethrough through which the workpiece is fed to the cutting assembly. This arrangement eliminates the need for costly drive arrangements and serves to substantially reduce the reciprocating mass of the apparatus thereby enabling a higher production rate while also increasing the overall realiability of the machine and hence its productivity.
The cutting assembly of the present invention comprises a plurality of single action pneumatically actuated pistons each having either a cutting blade or roller wheel fitted to an inner end thereof which operate to sever predetermined lengths of the workpiece. The centrifugal force resulting from continuous rotation of the cutting assembly operates to smoothly and quickly retract the pistons after the cutting operation has been completed thereby eliminating the need to employ double action piston assemblies or other retraction means which would increase the mass of the apparatus.
In one embodiment, the driving motor is provided with end plates having integrally formed guide means thereon so as to eliminate the need for additional adapter plates or other supporting structure to attach the driving motor to the reciprocating carriage assembly. Additionally, the motor shaft is adapted to enable the cutting assembly to be directly secured thereto so as to enable rapid changing thereof thus allowing relatively short set up times for changing between different size workpieces.
Additionally, in some applications it is desirable to reduce the possibility of the cutting assembly forming objectionable burrs on the inside diameter of the tubing. One method of accomplishing this objective is to subject the workpiece to transverse loading just before the cutting means has fully severed the workpiece so as to cause it to snap or break at the partial cut line. The present invention may also be provided with a stop assembly secured to and movable with the carriage assembly which includes means to apply such transverse loading to the workpiece. Not only does this optional stop assembly operate to insure a clean burr-free severing of the workpiece from the supply but also provides means for positively ejecting the severed workpiece from the apparatus so as to enable the next section to be moved into position without damage or jamming of the apparatus.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.